Many devices for administering a medicament are designed with a number of functions for providing ease of use for self-administration. The functions that are applicable comprise mixing of the medicament with a diluent, if the medicament is in powder form, priming of the medicament container, thereby reducing any air trapped therein, penetration of an injection needle into the tissue of a patient on an injection site, injection of a dose of medicament at the injection site, withdrawal of the injection needle after ended injection sequence and covering of the injection needle after use of the medicament delivery device.
Some medicament delivery devices require that a delivery member protrudes a certain length from the proximal end of the device when expelling a medicament through the delivery member. When using injection devices, some types of medicament require that the dose is injected at a certain depth into the tissue of the patient. Depending on the type of drug and/or treatment, the injection depth could be any of superficial, subcutaneous to intramuscular. In that respect, the injection depth also depends on the condition of the patient, i.e. the amount of fat in the subcutaneous tissue. Because of the demands on the penetration depth of the injection, devices have been developed that are arranged with mechanisms that can adjust the penetration depth.
The patent application No. PCT/EP2013/066542 discloses a medicament delivery device that is arranged with a needle shield arranged slidable in a longitudinal direction of the device. The proximal end of the needle shield is intended to be pressed against an injection site, whereby it slides in the distal direction, causing a penetration. The penetration stops when the needle shield hits a stop ledge or an abutment. In order to alter the penetration depth, the proximal end of the needle shield is provided with a penetration depth adjusting mechanism. It comprises a generally tubular part, a delivery member protruding adjuster, arranged with threads on its inner surface, arranged to cooperate with corresponding threads on the outer proximal surface area of the needle shield.
Thus, when the delivery member protruding adjuster is rotated in relation to the needle shield the penetration depth can be adjusted. In order for a user to be able to know the set depth, the outer surface of the needle shield is arranged with indicia such as numbers, for instance indicating penetration depth in millimetres. The indicia are then intended to cooperate with a marking or a cut-out on a distally directed end area of the delivery member protruding adjuster such that when the indicia and the marking are aligned, the depth indicated by the indicia has been set.
However, apart from the visual signs on the device it is sometimes difficult for a user to be sure that the proper penetration depth has been actually set. Also, there is a risk that the delivery member protruding adjuster is rotated accidentally prior to injection, causing the penetration depth to be altered. There is thus room for improvements in the area of penetration depth adjusting mechanisms for medicament delivery devices.